Add a legend to ggtree plot

Question

I'm using the R package ggtree to plot phylogenetic tree in R.

I have sucessfully produced the phylogenetic tree I was interested in, however, I have difficulties in adding a 'legend' to my figures.

I have tried the suggestions present in this post Add legend into ggtree (ggplot) R but it did not work. I did not find others.

Do you have any suggestion?

This is the command I'm running:

 plot<-ggtree(new.tree,layout=phylo_method)+geom_nodepoint(size=c(NA,size_node),colour=c(NA,col_node),pch=8,na.rm =TRUE)+
  geom_tiplab(align=FALSE, linetype='dashed', linesize=.3,size=2)+
  geom_tippoint(color=raxml_col, size=2, show.legend = TRUE)+
  theme(legend.position="right")